/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/MeshNormals.h
Looks through the normals for any that are zero, and tries to set them to the normal of some neighboring triangle, preferring the triangle on its longer side if possible. This is useful for finding connected components based on normals, as it prevents degenerate triangles with 0 normals from connecting otherwise disconnected components. This won't help if a whole mesh componenent is entirely made of such degenerate triangles (which is usually ok).
void SetDegenerateTriangleNormalsToNeighborNormal()